Add filetype support for WebAssembly text format

[rhysd]

Problem

Vim does not support WebAssembly text format

Solution

This PR adds support for the WebAsembly text format to Vim.

WebAssembly is a new executable format for browsers. Since WebAssembly spec is defined by W3C, the spec is one of long live web standards.

https://webassembly.org/

I had created a project vim-wasm to support the text format. And today, I refined it following WebAssembly Spec. Now it can highlight the text format very well.

This is an example of highlighting using my project vim.wasm:

[codecov-io]

Codecov Report

Merging #3264 into master will decrease coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3264      +/-   ##
==========================================
- Coverage   76.57%   76.55%   -0.03%     
==========================================
  Files          93       93              
  Lines      136843   136839       -4     
==========================================
- Hits       104793   104755      -38     
- Misses      32050    32084      +34

Impacted Files	Coverage Δ
src/gui_beval.c	55.02% <0%> (-6.56%)	⬇️
src/window.c	81.87% <0%> (-0.49%)	⬇️
src/gui_gtk_x11.c	48.03% <0%> (-0.15%)	⬇️
src/ex_cmds2.c	82.63% <0%> (-0.1%)	⬇️
src/normal.c	74.35% <0%> (-0.08%)	⬇️
src/undo.c	83.09% <0%> (-0.07%)	⬇️
src/screen.c	76.71% <0%> (-0.05%)	⬇️
src/edit.c	85.41% <0%> (-0.01%)	⬇️
src/misc1.c	84.29% <0%> (-0.01%)	⬇️
src/misc2.c	80.64% <0%> (ø)	⬆️
... and 6 more

---

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[brammool]

Linda wrote:

## Problem Vim does not support [WebAssembly text format][spec] ## Solution This PR adds support for the WebAsembly text format to Vim. WebAssembly is a new executable format for browsers. Since WebAssembly spec is defined by [W3C](https://www.w3.org/community/webassembly/), the spec is one of long live web standards. https://webassembly.org/ I had created a project [vim-wasm](https://github.com/rhysd/vim-wasm) to support the text format. And today, I refined it following [WebAssembly Spec][spec]. Now it can highlight the text format very well. This is an example of highlighting using my project [vim.wasm](https://github.com/rhysd/vim.wasm): <img width="424" alt="highlighting example" src="https://user-images.githubusercontent.com/823277/43366973-8377bdf8-9380-11e8-8ca7-a912768e6e10.png"> [spec]: https://webassembly.github.io/spec/core/text/index.html

Thanks for working on this. In the indent file you set the 'lisp' option. This has side effects. Instead, I would recommend to use the lispindent() function. Unless the side effects are actually desired. In the syntax file I would recomment setting 'cpo', like it's done in many. Even when you don't use line continuation, it also affects some details about regexp pattern matching.

…

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[rhysd]

@brammool Thank you for your quick reviews! I addressed the points at c4555b5

[brammool]

I'll include it, thanks. It would be nice to have your full name for the Maintainer line.

[rhysd]

@brammool

Thank you. I'll wait for the changes being included.

It would be nice to have your full name for the Maintainer line.

Yeah, I considered that, but I'm basically not making my full name public on the Internet. When my mind changes, I'll send a patch to update the 'Maintainer:' lines. Thank you for your suggestion.

[rhysd]

I confirmed these changes were included in master branch. Thank you.